Nerve Pathways

The axiallary nerve arises from C5-C6 nerve roots.

It exits the axilla via the quadrangular space with the posterior humeral circumflex artery. wrapping around the surgical neck of the humerus.

It splits into the anterior and posterior branches:
  • The anterior branch: wraps around the surgical neck of the humerus. It supplies the ant deltoid.
  • Posterior branch: supplies the teres minor and posterior deltoid muscle. supplies the lateral shoulder.

The median nerve arises from the C5-T1 nerve roots and the lateral and medial cords of the brachial plexus.

It exits the axilla inferior to the Teres Major.
It descends the arm initially lateral to the brachial artery and crosses to lie medial to the brachial artery prior to entering the antecubital fossa.
It exits the antecubital fossa by passing between the two heads of the pronator teres
In the forearm it gives of the Anterior Interosseous Nerve, which runs between the Flexor policis longus and flexor digitorum profundus.
The median nerve runs down the forearm between the Flexor digitorum profundus and superficialis.
The median nerve gives off the palmar cutaneous nerve and then continues to the hand via the carpal tunnel.
In the hand it terminates as the: Recurrent branch and Palmar digital branch

The musculocutaneous nerve arises from C5-C7.

It is a continuation of the lateral cord of the brachail plexus.
It emerges at the inferior border of the teres minor and pierces the coracobrachialis 5cm distal to the coracoid process.
It then runs between the biceps brachialis and brachialis supplying these two muscles.
It continues down the forearm as the lateral cutaneous nerve of the forearm. 

The radial nerve arises from C5-T1 nerve roots. It is formed from the posterior cord of the brachial plexus.

It exits the axilla via the triangular interval (bound by the long head of the triceps, humerus and teres major) 
It descends down the posterior compartment of the arm in the spiral groove of the humerus.
It peirces the lateral intermuscular septum and enters the forearm via the lateral antecubital fossa.
The radial nerve then pierces the supinator 3cm distal to the radial head. 
The radial nerve then splits into the superficial and deep branch witht the deep branch being the posterior interosseous nerve.

The Ulnar nerve arises from C8+T1 nerve roots and is a continuation of the medial cord of the brachial plexus.

It descends down the arm between the axillary artery and vein. With the artery lying lateral to it.
Half way down the forearm it then pierces the medial intermuscular septum to enter the posterior compartment of the arm.
It then passes posterior to the medial epicondyle.
Then passes through the two heads of the flexor carpi ulnaris passing down the forearm deep to this muscle.
It then gives off three branches:
  • Muscular branch
  • Palmar cutaneous
  • Dorsal cutaneous
It then passes into the hand superficial to the transverese capral ligament in Guyons cannal. Dividing into the:
  • Superficial – Plamar 1.5 fingers
  • Deep branch – intrinsic muscles
 

It arises from the L4-S3 nerve roots and lumbosacral plexus.

It exits the pelvis inferior to the piriformis in the majority of patients.
It then runs over the short external rotators and passes deep to the long head of the biceps femoris.
As it descends the posterior thigh it gives branches to supply the:
  • Adductor magnus (tibial)
  • Long head of biceps femoris (tibial)
  • Short head of biceps femoris (common peroneal component)
  • Semitendinous + semimembraneous
It then splits into the tibial and common peroneal nerve (variable location)
Runs into the popliteal fossa (semitendinous, semimembranous, biceps femoris (lat), med/lat head of gastrocnemius, fascia lata (roof), popliteus)

The obtruator nerve arises from the L2-L4 nerve roots

Lumbar plexus
Pierces the psoas major
Passes posterior to common iliac arteries
Through obtruator foramen.
Splits into anterior and posterior division.
Anterior devision cutaneous branch (anteriomedial thigh)
 
Posterior division supplies the adductor brevis and magnus
Anterior adductor longus, gracilis, pectineus

Arises from L2-L4 nerve roots.

It is from the lumbar plexus.
Enters/pierce the psoas major.
Runs under the inguinal ligament.
Enters the femoral triangle (inguinal ligament, sartorius, adductor longus, fascia lata roof).
4cm below the inguinal ligament it splits into the anterior and posterior division.
Anterior: sartorius, pectoneus
Posterior: saphenous nerve, quads femoris.